Chapter 14. Symmetric Encryption

In Chapter 13, we showed you how Alice can use data
hash codes to prevent Eve from secretly modifying the messages that
she sends to Bob. Hash codes are useful for message integrity, but
they do not provide any confidentiality; although Eve cannot alter
the messages from Alice without Bob knowing, she
is able to read the messages, and Alice and Bob
are unable to keep secrets from her.

In this chapter, we examine how to achieve confidentiality with data
encryption, and how to encrypt and decrypt data using the .NET
Framework. We also show you how to extend the .NET Framework by
adding a new encryption algorithm.